Directive radio system for guiding arrangements



Au hzs, 1942.

A. ALFORD 2,293,694

DIRECTIVE RADIO SYSTEM FOR GUIDING ARRANGEMENTS Filed Nov. 7, 1939 4Sheets-Sheet 2 was. w 101 116' 117 f j 14 F I65. X 115 5 121IR/l/VSM/i'if/P INVENTOR.,

AMP/76771446 F000 Aug. .25, 1942.

A. ALFORD 2,293,694

DIRECTIVE RADIO SYSTEM FOR GUIDINGARRANGEMENTS Filed Nov. 7. 1959 4Sheets-Sheet s l atented Aug. 25, 1 942 DERECTIVE RADIO SYSTEM FORGUIDING ARRANGEMENTS Andrew Alford, New York, N. Y., assignor toInternational Telephone & Radio Manufacturing Corporation, a corporationof Delaware Application November 7, 1939, Serial No. 303,206

18 Claims.

My invention relates to directive radio systems and more particularly todirective radio systems suitable for guiding beacons and similararrangements,

One form of radio beacon commonly used as a localizer beacon at anairplane landing field comprises an arrangement for producing a twodirectional guiding course along the direction of the landing runway. Insuch beacons it is desirable that the course be made quite sharp so asto avoid interferences due to reflection of energy from objects in thevicinity of the landing field. Should reflections occur from any suchobjects, distortion of the course and consequent errors in the guidingline may result.

It is an object of my invention to produce an array of radiant actingunits, either transmitters or receivers, for obtaining a sharp guidingline to reduce probability of such errors or to form a direction findingreceiver. This may be accomplished in accordance with the teachings ofmy invention by utilizing three radiant acting conductors spaced in aline and energized in suitable phase relation for producing the desiredpatterns for defining the guiding line.

A further difiiculty with guiding beacons when used for courselocalizers results from reflecting objects in the path of the backradiation causing variations in the front or principal guiding coursewhich will cause false courses usually termed multiple courses. Thistrouble may be reduced by constructing an arrangement such that theradiation in the direction of the principal objects causing thesedisturbances is reduced to a minimum.

It is accordingly 2. further object of my invention to design atransmitting array for guiding beacons wherein radiation in the backwarddirection is reduced or suppressed in directions toward reflectingobjects so as to obviate the above difficulties.

With radio beacons installed at particular landing fields it is oftendesirable to produce signals indicating the quadrant in which thereceiver is located with respect to the beacon so that the properdirection for landing may be readily attained.

It is also desirable that a particular signal identifying the landingfield be transmitted so that the pilot may be informed of the identityof the landing field.

, In accordance with further objects of my invention I provide means forproducing signals for quadrant identification at the localizer beacon 55 and may also provide means for identifying the particular landingfield.

In general, direction finders at present in use utilize the principle ofa single signal received on the crafts by means of a directive antennaesystem for indicating the direction line between the receiver and thetransmitting station.

In accordance with a still further object of my invention I provide asystem utilizing an antenna arrangement similar to that used for aguiding beacon for receiving signals from a broadcasting station so thata line of direction toward the station may be positively established.

Further objects and advantages of my invention will be apparent from theparticular description thereof made in accordance with the accompanyingdrawings illustrating a few preferred embodiments thereof, in which Fig.1 is a schematic diagram of a radio beacon v transmitter in accordancewith my invention,

Figs. 2, 3 and 4 are radiation diagrams used for explaining theoperation of the beacon of Fig. 1,

Fig, 5 is an illustration of a preferred type of antenna wherein radiantaction is obtained only for substantially purely horizontally polarizedraditions,

Fig. 6 illustrates a preferred embodiment of my invention for producinga two-course landing beacon,

Fig. '7 schematically shows a diagram of a twocourse beacon providedwith auxiliary means for reducing the radiation in certain directions,

Fig. 8 is a diagram illustrating the radiation patterns which may beobtained with the beacon system of Fig. '7,

Fig. 9 is a schematic illustration of a radio beacon in accordance withmy invention provided with means for producing quadrant identification,

Fig. 10 is a radiation pattern useful for explaining the operation ofthe system of Fig. 9,

Figs. 11 and 12 are alternative keying arrangements for use with thesystem illustrated in Fig. 9, and

Fig. 13 is a schematic diagram of a direction finding receiver utilizingthe principles of my invention.

Turning now to the drawings and particularly Figs. 1 to 4, a briefexplanation of the principles of my invention will be given. Throughoutthis discussion the explanation is made with respect to transmission ofsignals, it should be distinctly understood, however, that the sameprinciples apply to receiving systems, since receiving antennae operatesubstantially with the same type of radiant acting patterns as theradiation patterns of a transmitting system.

In Fig. 1 is illustrated a beacon comprising three vertical dipoles IOI,I02, I03. Each of these dipoles is tuned by means of correspondingtransmission line sections I 05, I06, I01. Antenna I! is arranged in thecenter and is energized over one diagonal of a hybrid bridge arrangementby energy from two sources II 0, I I I, modulated at two differentfrequencies F1, F2. The energy supplied to antenna IOI from the twosources is in phase. Energy is also supplied to the outer antennae I02,I03 over transmission lines H0, H1 from the same two sources of energyover the opposite diagonal of the bridge network IIE. By reason of thehybrid network the output terminals of sources IIO, III are independentof each other and similarly the loads connected over lines H4, and H6,H1 are independent one of the other. A 180 phase shift is provided intransmission line H6, for example by transposition II, so that antennaeI02, I03 are energized directly in phase opposition.

In order to explain the operation of the system we may first presumethat only antenna IOI is directly fed and that antennae I02, I03 areparasitically energized by radiation from I0 I. In such case a patternof dumbbell form, such as shown in Fig. 2, is obtained. The shape ofthis pattern may be varied by adjusting the spacing of parasiticallyenergized antennae I02, I03 with respect to the energized antenna IOI.Furthermore this shape may be modified by the variation in the tuning ofparasitic antennae I02, I03.

I have found that the preferred pattern forms may be obtained by spacingantennae I 02, I 03 substantially between 165 and 178 from radiator I 0|the preferred spacing being substantially 165. In this case the sectionsI06, I01 are made slightly longer than is necessary in order to tune theradiators to resonance, so that they are slightly inductive in reaction.

If now we energize antennae I02, I03 in phase opposition in such amanner that the phase relation of antennae I02, NH and I03 is 90, 0,+90, respectively, a radiation pattern is obtained somewhat of the formillustrated by the solid line curve 30 of Fig. 3, neglecting for themoment the effecting of direct energization of radiator IOI. When theenergization of the outer radiators is reversed so that an antenna I02is energized at +90 and antenna I03 at -90 with respect to antenna IN,the curve shown at 3i in dotted lines at Fig. 3 is obtained. This effectmay be produced in accordance with my invention by means of the bridgenetwork. Thus, energy from N0 is fed to antenna IOI directly, and is fedto antennae I02 and I03 in phase opposition over lines H6 and H1. Energyfrom source III is similarly fed directly to antenna IOI in phase but byreason of a 180 phase shifter I20 in network I I antennae I02, I03 areenergized in opposite phase with respect to the energy from source H0.Accordingly, the two patterns 30, 3I are simultaneously obtained, onemodulated with frequency F1 and the other with frequency F2. Thesepatterns superimposed with the dumbbell shaped pattern of antenna IOIproduce an overlapping radio beacon having two distinguishable patterns40 and III of Fig. 4. In this connection it is pointed out thattransposition I20 in network H5 should be so located that the carrierenergy from sources III), II I is not opposed in phase upon feeding toantenna IOI. Were the transposition I20 arranged at a point between thesources I I0, III and the antenna IOI, then the carrier would besubstantially suppressed on course. It is more satisfactory to have astrong carrier on course and for this reason the network should bearranged so that the carrier is not suppressed at antenna I 0 I.

As discussed above, it is pointed out that the radiation pattern of Fig.4 is obtained when the patterns of Fig. 2 and Fig. 3 are combined. Inorder that the combination may be properly made, it is desirable thatthe parasitic operation of antennae I02, I03 be preserved when thetransmission lines H6, I I1 are connected thereto for direct feeding ofthe energy. This may be accomplished by proportioning lines H6, H1 sothat they form a high impedance with respect to parasitic energy fromantenna IOI. Energy radiated from I III energizes antennae I02, I03 inphase, since it travels equal distances to the last named radiators. Theline I2I leading from the network to the junction point of lines H6, H1,is made preferably at the midpoint of these lines so that H6, II"! areequal in length. Accordingly, energy induced in antennae I 02, I03 fromIN, reaches the junction point of lines H6, H1 in phase oppositionbecause of the transposition in line H0. Therefore, this junction pointis at a voltage node which corresponds to a short circuit across thetransmission lines. If then, lines H6, III are each made equalelectrically to an odd number of quarter wavelengths long, then theywill present substantially infinite impedance to energy incoming fromantennae I02, I03 and will, therefore, have no effect upon the tuning ofthe transmission line sections I06, I01. Antennae I02, I03 will,therefore, operate as parasitic antennae in so far as the directenergization by radiation IOI is concerned, but will operate as fedantenna energized in phase opposition in so far as the feed over lineI2I is concerned. Accordingly, a radiation pattern of suitable sharpnessas shown in Fig. 4 will be obtained. By adjusting the connection pointsof lines H6, H1 on sections I00, I 01 the feeding of energy to antennaeI02, I03 may be controlled.

Because of the detuning of I06, I01 from resonance, a complete impedancematching of the transmission line is not obtained, although thearrangement produces very little mismatch. To match transmission lineswith respect to energy fed over line HI. I ma provide an impedancematching means such as element I25 connected across transmission lineI2I.

If, instead of making lines IIB, II1 of length L equal to an odd numberof quarter wavelengths, these lines are made equal to a multiple of ahalf-wavelength, then the junction points of these lines with sectionsI06, I01 will act as though there were a short circuit across thesections I61, so far as energy from IIJI is concerned. If thisconnection is made then the parasitic antennae I02, I03 may be tuned byadjusting the point of connection of lines H6, H1 thereto instead ofadjusting an actual short circuit bar. In this case the short circuitingbar must then be used for the purpose of adjusting the impedance orphase of the directly fed energy to radiators I02, I03. However, the oddquarter wavelength connection is considered preferable for this purpose.

The principles discussed in connection with Fig. l are generallyapplicable independently of the exact nature of the antenna used as theradiator.

A preferred form of antenna for use is illustrated in Fig. 5. Thisantenna unit is designed to produce substantially purely horizontallypolarized waves. The antenna unit is made up of four radiating arms 50to 53, inclusive, each of the arms 50 to 53 being of such a length thatfrom the feeding point 54 to the terminal end of the conductor issubstantially equal to a halfwavelength electrically. The outer ends ofthe conductors t to 53 are turned inwardly at their points adjacent theother conductors so that the radiant acting portion of each conductor isenergized substantially uniformly throughout. This type of antenna whenarranged in a horizontal position produces a substantially purelyhorizontally polarized radiation. For a more particular description ofthis type of antenna, reference is made to my co-pending applicationSerial No. 270,173, filed April 26, 1939.

In Fig. 6 is illustrated a beacon antenna similar to that shown in Fig.l but utilizing radiators of horizontally polarized waves of the typeillustrated in Fig. 5. In this figure, antennae IOI, I02 and H13 areconnected over lines H8, H1, HQ and I2l to a bridge network H5 over thebridge to a common transmitter 69 l. Transmitter Bill may be utilized inplace of the separate sources shown at H3, III in Fig. 1. The energyfrom this transmitter may be modulated by any known means illustrated as5&2, 563 to produce differently modulated waves for identifying thebeacon courses. This type of beacon transmitting horizontally polarizedwaves has been found to be successful for producing a sharp course alonga particular direction and one in which apparent shifting of the guideline is not caused by banking of the airplane. The sharpness of thecourse may be adjusted similar to the arrangement disclosed in Fig. 1 byadjusting the spacing and tuning of antennae W2, W3.

A further sharpening of the course may be obtained by arranging furtherparasitically excited antennae units EM, 605 on either side of thebeacon arrangement. The spacing between 604, 665 and I02, N13 ispreferably in the order of a quarter wavelength in an actualinstallation made wherein the beacon was operating at 109 meg-acycles.The spacing of the auxiliary parasitic antenna was made equal to 3' 6".The addition of these parasitic radiators tends to narrow down the widthof the radiation patterns so that the energy radiated from the beacondoes not diverge so much to either side thereof and therefore is lesssubject to reflection from nearby objects. Accordingly, the additionalsharpness of the course is enhanced as well-as a reduction indisturbances due to reflections in nearby objects.

When radio beacons of the type shown in Figs. 1 to 6, are located nearthe end of a landing runway, the radiations therefrom in one directionma be termed the forward course which the airplane follows in coming toa landing. The radiations in the opposite direction may be termed thebackward course or back course and serve merely to indicate to anaircraft the direction toward the landing field, but primarily forguiding the craft along the landing line. These back radiations,however, are generally subject to reflection to a higher degree than theforward radiations, since the beacon is usually located at one end ofthe field and nearby objects are more likely to be located in a regionof the back radiations. Reflection of energy from the back course intothe forward path causes distortions of the energy as received on theairplane and may produce several false or multiple courses. In.- orderto overcome this difficulty I provide a set of parasitic radiatorsarranged in the back of the beacon, as shown in Fig. 7. These additionalradiators may be utilized either with the three element beaconillustrated in Fig. 1, or with the five element beacon shown in Fig. 6.

In Fig. 7 the radio beacon itself is illustrated as being composed ofunits such as shown in Fig. 5. It should be understood, however, thatany type of radiator may be used therein. Similar reference charactersare used to apply to the elements of the main transmitter to those usedin Fig. 6. Directl behind radiators Hll, I92 and I03 are providedauxiliary parasitically energized antenna units 10!, I02, 103,respectively. These units are arranged preferably a distance in theorder of a quarter of the working wavelength, the exact distance beingsubject to adjustment dependent upon the angle at which the troublesomereflecting objects are to be found. In general this spacing is somewhatdiiferent from a quarter of a wavelength. Units Nil, 152, 103 are eachtuned substantially to resonance at the working frequency. This tuningmay be accomplished by adjusting short circuit bars on transmission linesections Hi, f 52 and 1 [3 connected to the respective antenna. As shownin the figure, transmission line sections H2, H3 are provided with aneffective or virtual short circuit, rather than real short circuitingbar.

Assuming first that units fill to Hi3 have been tuned to resonance andno further steps have been taken, it can be seen that energy fromradiator NH will operate to drive not only 10E arranged directly behindit but will also energize radiators W2, 163. Thus, the unit will not actto merely weaken the back course by reflection of energy at Nil, butwill cause distortions in the form of the back course as well. In orderto overcome this effect a transmission line is connected between units102, 153. In line 120 is provided a means, for example, a transpositionI21, for shifting the phase along this line. If line 126 is then madeequal to a half-wavelength long at the operating frequency, energyimpressed upon antennae 102, 103 in phase from radiator It! andparasitic antenna till, will then produce an apparent effective shortcircuit at the midpoint of this line. This short circuit will occur at apoint one-half wavelength from units m2, H63. Thus, the parasiticoperation of these units with respect to any phase energy from antennalfil and unit it! may be effectively avoided. Energy derived in units152, 103 and I02, E53, however, will be in phase opposition so that atthe midpoint of transmission line 120 a voltage loop will occur.Accordingly, the line 120 will operate as though the open ended halfwavetransmission line section were connected across the antenna and willpresent substantially infinite impedance. Accordingly, line I20 willhave no effect with respect to the energy induced from units I02, I03.In order to tune units 152, N33 to resonance, an additional shortcircuit may be provided, for instance, by means of the transmission line130. This transmission line is made equal to an integral multiple ofwavelengths and is not provided with a transposition. Accordingly,energy from H32, I03 impressed upon antennae 102, 103 will operate toproduce a virtual short circuit at the midpoint of 103 causing asubstantially similar effect at the junction points of line I30 withtransmission line sections H2, H3. By adjusting line 130 vertically withrespect to the antennae units I02, I03, these reflectors may be tuned tothe desired amount. In place of line 130 actual short circuiting barsmay be substituted.

In Fig. 7, lines I20 and I30, I20 is shown above line 130. It should beunderstood, however, that the relative positions of these lines may bevaried depending upon the actual tuning effects that are desired for theseparate units. Accordingly, each may be adjusted independently, itbeing merely necessary that the units be tuned to secure the desiredcancellation effect for the rear course. Likewise, it may be noted thatreflector unit MI is driven only from radiator IOI, since energyreaching it from the other radiators I02,

I03 will be directly in phase opposition. With the.

system as shown herein, tuning for the purpose of controlling thedirection patterns may be effected in any desired manner.

In Fig. 8 is shown, by way of example, a radiation diagram obtainedusing a system similar to that illustrated in Fig. 7. In this figure,00, I show the various patterns on each side of the course caused by theradiation from the beacon. The radiation fields are considerablyshortened due to the use of the reflecting antenna structure and may beadjusted to have a minimum, substantially at any desired angle 0,corresponding to the direction of the location of a reflecting object.Thus multiple courses due to reflections from the backward radiationsmay be substantially eliminated. It should be understood that this angle9 may be varied by the tuning and adjusting of the parasitic radiators10! to 103, inclusive, so as to assure neutralization of reflectedenergy from any particular direction.

In an actual test installation of apparatus in accordance with myinvention, an arrangement similar to that shown in Fig. 7 was madeutilizing three loops, that is, omitting the side parasitic reflectors600, 605. With this arrangement, elimination of troubles due toreflection from an object located at an angle of substantially 54 fromthe line of equal signal in the rearward direction was achieved. Theback course, however, still was of suflicient strength to extend anyusable quantities several miles to the rear of the airport.

With beacons utilized for guiding purposes it is often desirable thatmeans be provided for indicating on the aircraft if an approach is madeto the side of the beacon so as to indicate the presence of the landingfield in the vicinity. In accordance with my invention such anarrangement may be provided by use of a system such as illustrated inFig. 9. In this figure a beacon comprising three antennae IOI, I02, I03,is illustrated diagrammatically in plan view. This beacon may be similarto that shown in Figs. 1 or 5, and if desired, modulation identifyingthe courses may comprise low frequency signals, for example 90 and 150cycle signals. On either side of central radiator IOI are provided twoauxiliary antennae 90, 9|. These auxiliary antennae are preferablyparasitic loops and means for modulating or keying the energy byoperation on these loops is provided as indicated at 92. The loops 90,9!, may be arranged so that they are alternately tuned and detunedtending to reduce the energy radiated first in the forward and then inthe backward direction. The keying may be made in the form ofinterlocking Morse signals, for example, the well known AN signals maybe used. The operation of the system may be more clearly understood byreference to Fig. 10. In this figure the curves IOI4, IOI5 represent thepatterns produced when neither of the reflectors or 9| are efiective.When 90 is made effective, the patterns represented by curves IOI I,IOI3 are formed on each side of the course, so that the predominatingenergy is in the for- ,ward direction. When 90 is rendered inefiective,0| is rendered effective, the radiation pattern will then correspond tothe curves I000, I 0I2, producing a strong radiation in the backwarddirection and a weak radiation in the forward direction. This keying maybe accomplished in accordance with a known code so that in effectoverlapping equi-signal patterns are formed on each side of the beaconproducing in efiect another course. This course, however, is very wideand does not constitute a narrow guiding course but merely serves toindicate to the pilot that he is at one side of the beacon. However,when the pilot circles and approaches the beacon from either end he canthen maintain his course by means of the 90l50 cycle modulation and canidentify his direction of approach by the presence of a strong signalcorresponding to the keying frequency for that particular direction.

In Fig. 11 is illustrated one form of keying system suitable for usewith the arrangement of Fig. 9. In this figure, the two parasiticantennae 90, 9I, are shown connected over lines H00, IIOI to terminals.Movable contacts H02 are provided so as to connect a section oftransmission line H03 across either H00 or IIOI so as to tune and detunethe sections. Contact arms I I02 may be controlled by a relay H05 fromany known keying means such as indicated at I I06.

In Fig. 12 is shown a further embodiment of a keying means which may beused in accordance with my invention. In this figure the units 90 and SIare shown controlled by a keying means I200 which serves to alternatelyconnect lines I20I, I202, to a tuning transmission line I203 or to afurther control circuit indicated generally at I204. Movement of therelay contacts is controlled by relays I205, I 206, so that when antenna90 is connected to lin I 203, antenna 9| is connected to the circuitI204. This type of arrangement may be utilized with a beacon of the typeshown in Fig. 9, and may provide a further identifying signal forindicating the identity of the station. This additional means is thecircuit shown at I204 and comprises a pair of vacuum tubes I 2| 2connected in parallel to the contact terminals and energized from anaudio-frequency source I2I3 so that tubes I2I2 are alternately broughtand rendered conductive. Source I2I3 preferably operates at an audiofrequency, for example, 300 to 1000 cycles so that a particularfrequency identified with the station is alternately transmitted fromantennae 90, 9| in the direction of the stronger field of the course. Itis clear that if desired the identifying frequency may be applieddirectly as a modulation frequency to the beacon antennae IOI, I02, I03instead of being applied to the reflectors.

In event that a beacon is utilized wherein the main course is of thealternately energized type, for instance, the well known A-N beacon, theidentifying signals should be applied to the reflecting arrangement inthe manner shown in Fig. 12. In this manner the dot-dash frequency maybe applied to the reflectors 90, SI and simultaneously theidentification frequency may be applied thereto without interruptingeither of the courses. The line connecting the circuit I204 to theantennae 90, 9|, should preferably be made equal to substantially aquarter wavelength or odd multiple thereof electrically so that at thetime the tubes are blocked, the unit connected thereto is working intosubstantially an infinite impedance, Whereas when the tubes areunblocked the unit 9| is working into substantially zero impedance sothat a suitable modulation of the signals may be obtained.

Although, in the example illustrated, an array using only three units isshown, it should be understood that any of the arrays using five, six oreight antennae, as described in the foregoing portions of thespecification, may be used, depending upon the directive effect desired.

The antenna arrangement such as illustrated in Figs. 1, 6 and '7 may beutilized for the purpose of direction finding if desired, without anysubstantial change in the circuit other than the substitution of areceiver for the transmitter. One such arrangement is illustrated inFig. 13. In this figure the three antennae IOI, I02, I03 are showndiagrammatically as being of the type for receiving horizontal polarizedwaves, although it is clear that any type of antennae may be used. Theenergy received over antenna IOI and antennae I02, I03, are separatelyfed through a hybrid network to lines I3I0, I3II. In lines I3I0, I3I Ithen energy from the two sides of the course, as illustrated by thepatterns of Fig. 4, will be obtained. This energy may then be separatelydetected and the detected currents applied in opposing relation to anindicating instrument. However, it is usually necessary to amplify thereceived energy before a useful indication is obtained. In such a caseif the energy is to be directly compared, two separate amplifiers wouldnecessarily be provided in which case it is difiicult to assure equalamplification of both signals. Accordingly, a preferred form of receiveras shown in Fig. 13, constitutes modulating means I3I2, I3I3, in linesI3I0, I3II. The modulated energy is then fed over a conjugate networkI3I4 to an amplifying receiver I3I5 where the energy is amplified anddetected to produce the modulation envelopes. These output modulationenvelopes are then fed through device ISIS which constitutes a filterfor separating modulation waves and for rectifying these modulations,the rectified energy being then applied to indicator I3II. A balancingnetwork I3I8 is provided so that the conjugate bridge I3I4 may bemaintained balanced. With a receiver of this type it is clear thatwhenever the antenna is adjusted so that I02, I03 are equi-distant fromthe radiation source, equal signal output at the two frequencies will beobtained so that the meter will indicate the orientation of the antennagroup. If energy comes to the antenna group from either side, then thesignal corresponding to that side of the course will be received morestrongly than the other signal whereby an indication that the craft isnot traveling toward the station, will be obtained. It is clear thatmany other forms of this receiving apparatus utilizing the antennaarrangement of my invention may be built, it being merely necessary tokeep in mind that separation of the signals must be provided for at thereceiver.

Whle I have described a number of specific embodiments of my inventionin connection with the attached drawings, it should be distinctlyunderstood that these showings constitute merely a preferred structurein accordance with my invention. What I consider to be my invention isembodied in the accompanying claims.

What I claim is:

1. A directive radiant acting system comprising a. central radiantacting member, other radiant acting members on either side of saidcentral member and spaced therefrom a distance greater than a quarterwavelength at the working frequency, means for energizing said radiantacting members such that said central member produces radiant action andsaid other members produce radiant actions displaced 180 electricallywith respect to each other and displaced 90 electrically with respect tosaid central member, means for tuning said other members to oscillateparasitically with respect to cophasally supplied energy, translatingapparatus, and conjugate coupling means comprising a bridge network forcoupling said central member and said other members to said translatingapparatus independently of any interaction between said central memberand said other members.

2. A directive radiant acting system according to claim 1, wherein saidsystem operates as a radio beacon, said translating means comprising atransmitter and means for modulating said transmitted energy withdiiferent distinctive signals, further comprising means for applyingsaid separately modulated signals to said conjugate coupling means inconjugate relation, for feeding said central member and said othermembers.

3. A directive radiant acting system according to claim 1, furthercomprising parasitically energized radiant acting members arranged inspaced relation on the outer side of each of said other radiant actingmembers, whereby the directive sharpness of said system is increased.

4. A directive radiant acting system according to claim 1, furthercomprising a further parasitically energized radiant acting memberspaced from said central member in the direction substantially at rightangles to the line formed by said other members.

5. A directive radiant acting system according to claim 1, wherein saidtranslating means comprises a receiver and an indicator, separate inputcircuits for said receiver coupled to conjugate points on said conjugatecoupling means, Whereby energy from said radiant acting members isseparately supplied to said input circuits, and means in said inputcircuit for imparting dis- 7 tinctive characteristics to energy suppliedto said receiver from said circuits.

6. A directive radiant acting system according to claim 1, furthercomprising an additional central radiant acting member, other additionalradiant acting members arranged on either side of said additionalcentral radiant acting member, said additional radiant acting membersbeing spaced in the same direction from corresponding ones of saidradiant acting members, means for tuning each of said additional radiantacting members to resonance for parasitic energization fromcorresponding radiant acting members, and means for detuning said otheradditional radiant acting members from resonance for energy derived fromsaid central members.

7. A directive radiant acting system according to claim 1, furthercomprising additional radiant acting members arranged on opposite sidesof said central radiant iacting member and spaced therefrom, and meansfor alternately tuning said additional radiant acting members toresonance at the working frequency.

8. A directive radiant acting system according to claim 1, wherein saidsystem constitutes a transmitting radio beacon, further comprisingadditional radiant acting members arranged on opposite sides of saidcentral radiant acting memher and spaced therefrom, means for alternately tuning said additional radiant acting members to resonance at theworking frequency, and means for imparting to said beacon a furthersignal for identifying said transmitter.

9. A radio beacon comprising means for radiating overlapping fieldshaving distinctive signal characteristics in each of two directions todefine a course line, reflector means spaced on both sides of saidradiating means in the direction of said course line on opposite sidesof said radiating means, and means for rendering said reflector meansalternately effective in predetermined relation to identify the oppositesides of said course line.

10. A radio beacon comprising a first radiator, a pair of radiatorsspaced a distance between a quarter wavelength and a half wavelength atthe working frequency on either side of said first radiator, a fourarmed bridge network, means for connecting said pair of radiators inphase opposition to an apex of said network, means for connecting theopposite apex of said bridge network to said first radiator, a pair ofenergy sources of the same frequency modulated with distinctive signals,means for connecting said energy sources to respectively oppositecorners of said network whereby energy from said sources is fed to saidfirst radiator cophasally and to said pair of radiators in phaseopposition, means for phasing the energy from one of said sources inphase opposition to the energy from the other source in said pair ofradiators, and means for tuning said pair of radiators to oscillateparasitically with respect to energy absorbed cophasally.

11. A radio beacon according to claim 10, further comprising a firstreflecting antenna and a pair of reflecting antennae spaced therefromand spaced from said respective ones of said radiators, means for tuningsaid reflecting antennae to the operating frequency for parasiticenergization from the corresponding radiator, means detuning said pairof reflecting antennae with respect to cophasal energization from saidfirst radiator whereby parasitic action from this source is eliminated,and means for transmitting from said beacons further signals foridentifying said beacon.

12. A radio beacon according to claim 10, further comprising a firstreflecting antenna and a pair of reflecting antennae spaced therefromand spaced from said respective ones of said radiators, means for tuningsaid reflecting antennae to the operating frequency. for parasiticenergization from the corresponding radiator, and means detuning saidpair of reflecting antennae with respect to cophasal energization fromsaid first radiator whereby parasitic action from this source iseliminated.

13. A radio beacon according to claim 10, further comprising areflecting antenna system spaced from said beacon radiators, said systemcomprising three antennae corresponding to respective radiations,adjustable means for tuning said antennae for parasitic operation asreflectors, and adjustable conductor means physically a multiple ofwavelengths long and electrically an odd multiple of wavelengths longinterconnecting the tuning means to said antennae corresponding to saidpair of radiators, whereby an ef fective short circuit may be producedfor detuning said antennae with respect to cophasal parasiticenergization.

14. A radio beacon according to claim 10, further comprising parasiticantennae spaced from said first radiator on opposite sides thereof andsubstantially equi-distant from the radiators of said pair of radiators,means for tuning and detuning said antennae alternately to produceinterlocking signals transversely of the course defined by said beacon.

15. A radio beacon according to claim 10, further comprising parasiticmeans spaced from said first radiator on opposite sides thereof andsubstantially equi-distant from the radiators of said pair of radiators,means for tuning and detuning said antennae alternately to produceinterlocking signals transversely of the course defined by said beacon,and means for imparting to said antennae a distinctive audio frequencymodulation for identifying the station during the detuned alternateperiod thereof.

16. A radio direction finder comprising an energy receiving antennasystem including, a first antenna, and other antennae spaced on eitherside of said first antenna, a bridge network having four arms, one ofsaid arms being electrically half a Wavelength greater than the otherarms, means connecting said first antenna to one corner of said bridge,means connecting said other antennae in phase opposition to thediagonally opposite corner of said bridge, transmission lines connectedrespectively to the other diagonally opposed corners of said bridge,means for imparting distinctive characteristics to energy received fromsaid antenna system in said transmission lines, and means responsive tothe received energy with said different characteristics for indicatingthe orientation of said antenna system with respect to a source ofreceived energy.

17. A radio direction finder comprising an energy receiving antennasystem including, a first antenna, and other antennae spaced on eitherside of said first antenna, a bridge network having four arms, one ofsaid arms being electrically half a wavelength greater than the otherarms, means connecting said first antenna to one corner of said bridge,means connecting said other antennae in phase opposite to the diagonallyopposition corner of said bridge, transmission lines connectedrespectively to the other diagonally opposed corners of said bridge,means for detecting the energy impressed in said transmission lines, andmeans responsive to the detected energy for indicating the orientationof said antenna system with respect to a source of received energy.

18. A radio direction finder according to claim 16, further comprisingmeans for amplifying and detecting said distinctively characterizedenergy and means for separating said detected energy in accordance withsaid distinctive characteristics interposed between said means forimparting distinctive characteristics and said means for indicating.

ANDREW ALFORD.

